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US6636616B1
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Method and apparatus for digital watermarking using error diffusion
Assignee: Xerox Corp
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Filing: 1999-11-30
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Granted: 2003-10-21
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Expires: 2019-11-30
Abstract
Abstract A method is described to imbed hidden information in output images that are rendered using error diffusion. The idea is to introduce a bias in the dot placements and then modulate that bias with the pattern to be hidden. The method particularly involves the steps of rendering the output copy using an error diffusion routine that parses through a plurality of stored pixels representing an image; modifying the error diffusion routine with a biasing pattern that influences where on the output copy each of the plurality of pixels is rendered; and further modifying the error diffusion routine with a watermark pattern that modifies the biasing pattern for pixels that are positioned within the watermark.
Inventors
- 👤 Steven J. Harrington
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 20:17
CPC Classifications
G; G06; G06T; G06T1/00; G06T1/0021; G06T1/005; G06T2201/00; G06T2201/005; G06T2201/0051
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
108 words
A method for imbedding a watermark in an output copy, the method comprising the steps of: a) providing an image representation defined by a plurality of pixels; b) comparing a first pixel intensity value to a threshold value; c) rendering a dot on an output copy, the dot having a second intensity value based on the comparison of step b); d) distributing a difference between the first and second intensity values among a plurality of pixels located proximate the first pixel; e) modifying the threshold value with a biasing value and a watermark value; and f) repeating steps a) through e) for each of the plurality of pixels.
Claim 2
Independent Claim
108 words
A method for imbedding a watermark in an output copy, the method comprising the steps of: a) providing an image representation defined by a plurality of pixels; b) comparing a first pixel intensity value to a threshold value; c) rendering a dot on an output copy, the dot having a second intensity value based on the comparison of step b); d) distributing a difference between the first and second intensity values among a plurality of pixels located proximate the first pixel; e) modifying the threshold value with a biasing value and a watermark value; and f) repeating steps a) through e) for each of the plurality of pixels.
Claim 3
Dependent Claim
21 words
The method of claim 1 , wherein step e) includes the step of: obtaining the watermark value from a look-up table.
Claim 4
Dependent Claim
25 words
The method of claim 1 , wherein step e) includes the step of: obtaining the biasing value from a high-frequency pattern with a zero mean.
Claim 5
Dependent Claim
21 words
The method of claim 1 , wherein step e) includes the step of: obtaining the biasing value from a look-up table.
Claim 6
Dependent Claim
21 words
The method of claim 1 , wherein step e) includes the step of: obtaining the biasing value from an analytic expression.
Claim 7
Dependent Claim
21 words
The method of claim 5 , wherein the biasing value is obtained from the expression: B *(( x %2)*2−1)*(( y %2)*2−1)).
Claim 8
Dependent Claim
24 words
The method of claim 1 , further including the step of: g) superimposing a biasing pattern on the output copy to view the watermark.
Claim 9
Independent Claim
95 words
A method for imbedding a watermark in an output copy, the method comprising the steps of: a) providing an image representation defined by a plurality of pixels; b) obtaining a biasing value from a high-frequency pattern with a substantially zero mean; c) rendering a pixel based on a threshold value, the biasing value, and a watermark value; d) modifying the threshold value by the biasing value and the watermark value to influence whether a dot is generated in the output copy; and e) repeating steps b) through d) for each of the plurality of pixels.
Claim 10
Independent Claim
95 words
A method for imbedding a watermark in an output copy, the method comprising the steps of: a) providing an image representation defined by a plurality of pixels; b) obtaining a biasing value from a high-frequency pattern with a substantially zero mean; c) rendering a pixel based on a threshold value, the biasing value, and a watermark value; d) modifying the threshold value by the biasing value and the watermark value to influence whether a dot is generated in the output copy; and e) repeating steps b) through d) for each of the plurality of pixels.
Claim 11
Independent Claim
106 words
A method for imbedding a watermark in an output copy, said method comprising: a) providing an image representation defined by a plurality of pixels; b) rendering a pixel based on a threshold value, a biasing value, and a watermark value, wherein the biasing value satisfies the expression: B *(( x %2)*2−1)*(( y %2)*2−1)); c) modifying the threshold value by varying at least one of the biasing value and the watermark value to influence whether a dot is generated in the output copy; and d) repeating steps b) and c) for each of the plurality of pixels, such that the watermark is hidden within the output copy.
Claim 12
Independent Claim
106 words
A method for imbedding a watermark in an output copy, said method comprising: a) providing an image representation defined by a plurality of pixels; b) rendering a pixel based on a threshold value, a biasing value, and a watermark value, wherein the biasing value satisfies the expression: B *(( x %2)*2−1)*(( y %2)*2−1)); c) modifying the threshold value by varying at least one of the biasing value and the watermark value to influence whether a dot is generated in the output copy; and d) repeating steps b) and c) for each of the plurality of pixels, such that the watermark is hidden within the output copy.
Claim 13
Dependent Claim
21 words
The method of claim 9 , wherein step c) includes the step of: obtaining the watermark value from a look-up table.
Claim 14
Dependent Claim
22 words
The method of claim 9 , wherein obey step c) includes the step of: obtaining the biasing value from a look-up table.
Claim 15
Dependent Claim
24 words
The method of claim 9 , further including the step of: e) superimposing a biasing pattern on the output copy to view the watermark.
Claim 16
Independent Claim
101 words
A method for imbedding a watermark in an output copy, the method comprising the steps of: a) storing an image representation defined by a plurality of pixels; b) rendering the output copy using an error diffusion routine that parses through the plurality of stored pixels; c) modifying the error diffusion routine in step b) with a biasing pattern that influences where on the output copy each of the plurality of pixels is rendered; and d) further modifying the error diffusion routine in step b) with a watermark pattern that modifies the biasing pattern for pixels that are positioned within the watermark.
Claim 17
Independent Claim
101 words
A method for imbedding a watermark in an output copy, the method comprising the steps of: a) storing an image representation defined by a plurality of pixels; b) rendering the output copy using an error diffusion routine that parses through the plurality of stored pixels; c) modifying the error diffusion routine in step b) with a biasing pattern that influences where on the output copy each of the plurality of pixels is rendered; and d) further modifying the error diffusion routine in step b) with a watermark pattern that modifies the biasing pattern for pixels that are positioned within the watermark.
Claim 18
Dependent Claim
31 words
The method of claim 13 , wherein step d) includes the step of: further modifying the error diffusion routine in step b) with a watermark pattern stored in a look-up table.
Claim 19
Dependent Claim
30 words
The method of claim 13 , wherein step c) includes the step of: modifying the error diffusion routine in step b) with a high-frequency biasing pattern having a zero mean.
Claim 20
Dependent Claim
30 words
The method of claim 13 , wherein step c) includes the step of: modifying the error diffusion routine in step b) with a biasing pattern stored in a look-up table.
Claim 21
Dependent Claim
30 words
The method of claim 13 , wherein step c) includes the step of: modifying the error diffusion routine in step b) with a biasing pattern generated from an analytic expression.
Claim 22
Dependent Claim
24 words
The method of claim 13 , further including the step of: e) superimposing the biasing pattern on the output copy to view the watermark.
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